Drug infusion with pressure sensing and non-continuous flow for identification of and injection into fluid-filled anatomic spaces

ABSTRACT

An automatic injection apparatus uses non-continuous fluid-flow of drugs to identify an intended injection site and includes a drive mechanism, a sensor and a controller for establishing fluid flow and pressure and preventing fluid flow until the pressure drops below a predetermined threshold. The pressure threshold is determined based on an internal pressure generated during an injection and more fluid will not flow until it drops below a predetermined pressure. An injection is performed to establish an initial pressure threshhold and then to stop the fluid flow into a patient until the pressure drops below a predetermined pressure which allows fluid flow to resume, thus identifying a fluid filled tissue space. The initial pressure threshold is used as a control parameter to a microprocessor below which controls the rate of injection. Fluid flows below certain pressures are also used to identify a specific location within the body during injections.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates generally to improvements to the deliveryof drugs, particularly to systems for subcutaneous injection/aspirationinto a fluid filled space of the body. More specifically the inventionprovides a method and device to identify a fluid-filled tissue space ofthe body by stopping fluid flow based on a predetermined pressuremeasurement and resuming fluid flow once the pressure drops below apredetermined pressure measurement.

A regional anesthesia block of epidural tissue-space is understood toproduce effective transient anesthesia of the lower extremities of thebody. It can be effectively used for a vast number of invasiveprocedures of the body, including but not limited to child birth,prosthetic hip replacement and a variety of other surgical procedureswhere anesthesia below the waist is required. It can also be effectivelyused for treatment of chronic and acute pain including, for example,“back-pain,” ailments of the vertebrae and, compression of the accessorynerves of the spinal column. To achieve effective regional anesthesiaand to block nerve transmission to the CNS an adequate volume of a localanesthetic solution must be deposited in close proximity to the spinalcord at a particular level of the vertebral column within the anatomicsite known as the epidural “space.”

The epidural space is that part of the vertebral canal not occupied bythe dura mater and its contents. It lies between the dura and theperiosteum lining the inside of the vertebral canal. It extends from theforamen magnum to the sacral hiatus. The anterior and posterior nerveroots in their dural covering pass across the epidural space to unite inthe intervertebral bodies, and the intravertebral discs. Laterally, theepidural space is bordered by the periosteum of the vertebral pedicles,and the intervertebral foramina. Posteriorly, the bordering structuresare the periosteum of the anterior surface of the laminae, the articularprocesses and their connecting ligaments, the periosteum of the root ofthe spines, and the interlaminar spaces filled by the ligamentum flavum.The space contains venous plexuses and fatty tissue which is continuouswith the fat in the paravertebral space.

The epidural fluid filled space (posterior epidural space) is a limitedanatomic area with an irregular shape measuring in several squaremillimeters with respect to cross section of the vertebrae and spinalcolumn. The fluid filled space is very narrow and is associated closelywith the dura of the spinal column with the ligamentum flavum closelyadjacent. The fluid filled space therefore has to be clearly identifiedwhen the bevel or point of the needle exits the ligamentum flavum, asthe dura will be punctured if the needle continues to penetrate. Thestandard technique for locating the epidural fluid filled space employsthe “loss-of-resistance” technique. This technique utilizes alow-friction syringe made of plastic or glass connected to an epiduralTouhly needle (16 to 18 gauge).

The block can be performed with the patient either in the sitting orlateral decubitus position. The patient should be encouraged to adapt acurled up position, as this tends to open the spaces between the spinousprocesses and facilitates the identification of the intervertebralspaces. Epidural injections can be sited at any level along the lumbarand thoracic spine, enabling its use in procedures ranging from thoracicsurgery to lower limb procedures.

The clinician palpates the vertebral column at the appropriate level ofthe vertebral column between vertebrae. Local anesthesia is placedwithin the superficial tissues rendering the tissues of the area to belocally anesthetized. The dermis is then punctured using the Touhlyneedle and the needle is advanced while the clinician simultaneouslyapplies pressure on the plunger of the syringe. The pressure on theplunger will unintentionally result in an amount of fluid continuouslyexiting out of the needle within the tissues.

Insertion of the epidural needle continues and advances through thesupraspinous ligament, with the needle pointing in a slightly cephaladdirection. The needle is advanced into the interspinous ligament, whichis encountered at a depth of 2-3 cm, until the subjective sensation ofincreased resistance is felt as the needle passes into the ligamentumflavum. The needle is further advanced until the subjective “feel” ofresistance by the clinician results in a distinct “back-pressure” on theplunger. The clinician must subjectively differentiate the“back-pressure” or resistance encountered to identify the location ofthe anatomic structure of the ligamentum flavum. The epidural fluidfilled space is entered by the tip of the needle after it passes throughthe ligamentum flavum.

A known deficiency of this technique is loss of fluid into the tissueswhen the tip of the needle is in the interspinous ligament as thetissues there are not particularly dense.

The movement of the Touhly needle from penetration of the dermis toidentification of the ligamentum flavum can vary from greatly in depthdepending on the patient's physical size. Overweight patients present agreater challenge, and with the morbidly obese patient it may not be asuitable technique because of the limitations of subjective nature ofthis technique. Age appears to be an additional complicating factorbecause of the challenge presented by the reduced size of the anatomy ofthe epidural tissue-space. Small children are often subject to the moredangerous procedure of general anesthesia as a result.

Unfortunately, if the epidural procedure is not performed properlyadditional fluid is injected within the tissues indiscriminately whiletrying to determine the location of the fluid-filled epidural space. Theadditional fluid released into these tissues can further complicate theidentification of the fluid-filled space.

Additionally, if the Touhly needle moves once the epidural space hasbeen located, either by removal of the syringe or inadvertent movementof the patient or doctor's hand, the needle can either be unknowinglymoved outside the epidural tissue-space or at worst advanced into duraof the spinal cord producing what is termed a “wet-tap”, which can havea dangerous long-term consequences to the patient. Even if the epiduralspace was initially properly located, if the needle further advancesduring the injection of the anesthetic solution it may deposit a bolusof anesthetic solution into the spinal cord resulting in transient orpermanent nerve damage.

Infusion pumps devices and systems are well known in the medical arts,for use in delivery or dispensing a prescribed medication to a patient.Several attempts have been made to adapt these devices for theadministration of an epidural injection.

Prior art references are known which attempt to utilize a pressuretransducer to measure the pressure within the syringe (see U.S. Pat. No.5,295,967 to Rondelet et al.). A major deficiency of these systems istheir inability to adjust the flow rate and/or pressure of the fluid tocompensate for changes in resistance throughout the system.

U.S. Pat. No. 7,922,689 to Lechner discloses a device for locating ananatomic cavity that rely on an alarm (i.e. audible or visual warningsignal) requiring the operator to manually modulate the drug deliverysystem during an injection procedure. This device requires thecontinuous flow of fluid to identify the epidural tissues similar to the“loss-of-resistance” manual syringe technique. In addition, it reliesupon a relative audible change related a pressure drop to identify theepidural tissues. The device requires subjective interpretation ofevents to which the operator must respond. Furthermore, the deviceprovides continuous injection fluid delivery and attempts to generate asufficient pressure to do so via an automatic syringe pump device. Thedevice does not, however, provide a means for automatically controllingthe injection pressure of fluid delivery or for aspiration of drugdelivery during use. Thus, the device of U.S. Pat. No. 7,922,689maintains injection flow rate despite excess fluid pressure that mayresult in pain and/or tissue damage.

The concept of using pressure as a metric to perform a safe andeffective epidural injection has been well documented in the medicalliterature. Pressure has been used to identify the epidural space andthe importance of pressure within the epidural space has been describedby a number of researchers over the years utilizing a variety ofexperimental set-ups. Usubiaga and co-workers discussed the relationshipof pressure and the epidural space while performing an injection intothe epidural space and tissues (Anesth. Analg., 46: 440-446, 1967).Husenmeyer and White described the lumbar epidural injection techniqueand relationship of pressure of during injection in pregnant patients(Br. J. Anaesth., 52:55-59, 1980). Other investigators, including Pauland Wildsmith (Br. J. Anaesth., 62:368-372, 1989) and Hirabayashi et al.(Br. J. Anaesth., 1990 65:508-513), also evaluated the relationshipsbetween pressure and the effects of resistance on the administration ofan epidural injection. Lakshmi Vas and co-workers have extended theseprinciples into the area of pediatric medicine (Pediatric. Anesth.11:575-583, 2001). Lechner and co-workers described a system for manualmanipulation epidural injections based on pressure feedback (Anesthesia,57:768-772, 2002; Anesth. Analg. 96:1183-1187, 2002; Euro. J.Anaestheol. 21:694-699, 2004).

The invention herein described improves the reliability and safety ofepidural injection administration by limiting the fluid required toidentify the epidural space. It also improves upon prior techniques byproviding a predetermined pressure limit and a predetermined resumptionof fluid flow below said pressure limit. Additionally, audible and/orvisual signal information is provided when the system resumes fluid flowthereby detecting needle entry into the fluid filled space of epiduralregion.

U.S. Pat. No. 6,200,289 to Hochman et al., co-invented by the inventorof the subject application and incorporated herein by reference,discloses an automatic injection device that includes a drive mechanismthat causes a therapeutic fluid to flow from a cartridge supported by acartridge holder, a tube and a handle with an injection needle. Thedrive mechanism is connected to an electric motor and a sensorpositioned at the motor output that measures the force applied by themotor to the drive mechanism. This force is then used to determine aninternal characteristic such as a force or internal pressure generatedduring the injection process. This characteristic is then used as acontrol parameter by a microprocessor or controller which generatescorresponding commands to the drive mechanism. In a particularlyadvantageous embodiment, the characteristic is used to calculate an exitpressure at which fluid is ejected by the device through an elongatedtube. The electric motor is then operated in such a manner that the exitpressure is maintained at a predetermined level to insure that a patientdoes not suffer pain and/or tissue damage.

Published patent application US2011/0120566 to Ohmi et al. is from thenon-analogous field of non-biological fluid supply methods forsemiconductor manufacturing, chemical industrial and medical industrialfacilities. The reference is sited, however, for its teaching ofdiscontinuous switching of fluid flow rate using a pressure type flowrate control device. The probing of anatomic space is not contemplatedand the person skilled in the art of designing medial treatmentapparatuses and methods would not look to this non-analogous art forguidance.

Published patent application US2011/0301500 to Maguire et al. disclosesan automated vessel puncture device using three-dimensional nearinfrared imaging and a robotically driven needle to providingsimultaneous real-time diagnostic assays. It teaches that venipunctureis the process of obtaining a sample of venous blood for purposes ofperforming various tests. Samples are obtained manually from a vein ororgan that is close to the surface of the skin by trained personnel, butthere are problems inherent with these processes. This reference usesinfrared imaging and a robotically driven needle to address the problembut does not use fluid pressure values to help indication the presenceof vein or organ. Although pressure is mentioned, this refers tomechanical pressure resisting the movement of the mechanically drivenneedle to avert injury to the patient, not to fluid pressure in theneedle.

Also see published U.S. patent application US2006/0122555 to Hochman,incorporated herein by reference, which discloses an in-line fluidpressure sensor between a syringe and tubing connected to a needle forinjecting the fluid.

Other patents that disclose the use of a mechanical biasing force(rather than a transducer) to locate and control the flow of a fluid areU.S. Pat. Nos. 8,197,443 and 8,137,312 for detection apparatuses andmethods.

Also see U.S. Pat. No. 8,142,414 for methods of injecting fluids intojoints using a handpiece assembly, U.S. Pat. No. 8,079,976 for anarticular injection system and published patent applicationUS2006/0122555 for a drug infusion device for neural axial andperipheral nerve tissue identification using exit pressure sensing.

Additional more recent work of Lechner is also disclosed in his patentapplications US2012/0101410 for unit, assembly, device and method fortesting a sensor means provided in a medical localization device andUS2012/0022407 for device for locating a structure inside a body.

A need remains for an apparatus and method that can accurately guide theinsertion of a needle into a fluid-filled anatomic space having a lowerpressure than its surrounding tissues, such as the epidural space nearthe spine, the intra-articular space in joints, fluid filled vessels ofthe body, and which apparatus and method can control both injection offluid into and aspiration of fluid from the epidural space, and whichapparatus and method further address the need for maintaining a sterilefield and sterile conditions.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus or device that enables the practitioner to accurately andreproducibly administer an injection to a patient in a desiredfluid-filled tissue location. The device and method limit the amount ofpain and tissue damage associated with the injection, the risk ofcomplication from a misplaced injection, and, of critical importance,significantly reduce the amount of injection fluid that is administeredto non-target tissues. The device utilizes the inherent differences intissue density or resistance of fluid-filled tissue space and associatedpressures which are significantly lower than surrounding organs,connective tissue or other tissues of the body.

Connective tissues of the body have been shown to produce pressuresabove 200 mm/Hg when injected with a fluid at a rate of 0.07 mL/sec.Each tissue has its own pressure density characteristics which arerepresented as measurable pressures that can be elicited within a giventissue type. The density or resistance of the tissue is measured usingthe pressure of a fluid infused from a computer-controlled drug deliverysystem capable of detecting pressure resistance during infusion. It hasalso been demonstrated that fluid-filled spaces such as the epiduraltissues, the intra-articular space of joints, or vessels of the bodyhave pressures when measured during injection which are well below 200mm/Hg. In fact, fluid-filled spaces have been found to havesignificantly lower pressure resistance to fluid-flow closer to zeromm/Hg when infusing into this fluid-filled tissue sites.

Based on the known understanding of an injection with an intended targetsite of fluid-filled tissue space one can identify the intended site byusing a pressurized fluid injection system that will not allowfluid-flow to occur until the needle enters into a fluid-filled tissuespace allowing the pressure to drop below a said predetermined pressurewithin the tissues. The device, by using a predetermined maximumpressure value which automatically prevents continuous drug flow intosurrounding tissues and will only resume drug flow once the pressuredrops below a further predetermined value, enables the identification ofa fluid-filled space based on the resumption of fluid-flow during aninjection.

The device can utilize a single or two different predetermined pressures(e.g. a first and third pressure) to stop fluid flow and another (e.g.second) predetermined pressure to resume fluid flow during an injection.It is also possible that the first predetermined pressure is used tostop fluid-flow and the second predetermined pressure is selected toresume fluid-flow once the identification of a fluid-filled space isachieved. Both will effectively limit the placement of a fluid intounintended tissues by eliminating the need for a continuous flow offluid during the placement of a needle and allow the identification of afluid-filled space once the resumption of fluid-flow occurs withinpatient tissues. It is also possible to include the third predeterminedpressure which can stop fluid-flow at a determined pressure limit whichis lower than the first predetermined pressure limit described above.This provides an even greater level of safety for the injection of afluid if the needle should migrate out of the target during an injectionto the patient.

Thus, an injection device of this invention includes a fluid reservoir(fluid storage device), an injection fluid, a pumping mechanism, an endin fluid contact with the reservoir and adapted to be inserted into thebody of a patient, a sensor arranged to determine a resistancemeasurement of the injection fluid, and a controller capable ofreceiving the resistance measurement from the sensor, calculate apressure, and modulating the flow rate of the injection fluid. Thesensor may be an in-line sensor placed between the pumping mechanism andthe end, but is preferably between the pumping mechanism or syringe andthe beginning of the tubing set which measures the pressure of theinjection fluid. Alternatively, the sensor may be within the mechanicalarm.

A sensor, such as a transducer, is used to sense the force or pressuregenerated by the motor and applied by the plunger within the fluidstorage device. In one aspect of the invention, the transducer measuresthe force between the carpule adapter and the remaining housing of thedevice. In another aspect of the invention, the transducer includes asize sensing device that senses a change in dimension of an element ofthe device, said change being indicative of the force or pressure of thedrug within the system and the pressure. For example, the change in sizeof the tubing may be used as an indicia of this force or pressure. Inanother embodiment, the pressure within the tube is measured externallyand used as a means of determining the fluid pressure.

It is contemplated that the controller is capable of acceptinguser-inputted parameters including, for example, a pre-set maximumpressure, a pre-set resumption pressure and a pre-set flow rate. Thecontroller is further capable of modulating the flow rate, includingreducing the flow rate to substantially zero. The flow rate may becontrolled in a binary manner (i.e., at a pre-set flow rate when themeasured pressure is less than the pre-set maximum pressure, and offwhen the measured fluid pressure is less than the pre-set maximumpressure), or the flow rate may be a function of the pressure (i.e., theflow rate is higher at measured pressures farther below the pre-setmaximum pressure). In the latter case, the flow rate may, optionally, bepreset to a maximum allowable flow rate. Likewise, the function relatingthe flow rate to the measured fluid pressure may also be user-defined.In useful embodiments, the pre-set maximum pressure is between about 50mm/Hg and about 300 mm/Hg, or between about 100 mm/Hg and about 250mm/Hg.

The pressure resistance measure is optionally converted into a visual aswell as audible signal on a continuous basis. The measurements are thenpresented to the doctor so that the doctor can determine or confirmwhether the injection is being delivered to the correct tissues. Inaddition, the measurements are also recorded for later review anddocumentation of the clinical event. Upper limits of pressure as well ascontrol of flow-rate can be pre-defined to ensure that excessivepressure and/or flow-rate are not used during this process.

The invention, therefore, provides a method for administering aninjection to a patient by providing a fluid reservoir, an injectionfluid, a pumping mechanism, and an end adapted for insertion into thepatient; pumping the fluid from the reservoir into the patient;calculating the pressure of the fluid at an interface between the endand the tissue of said patient, and controlling the flow rate of theinjection fluid such that the pressure does not exceed a pre-set maximumpressure and then the flow rate resumes once the pressure drops below apre-set pressure.

In one embodiment, the devices and methods of this invention are used toadminister an epidural injection. In a second embodiment, the device andmethod of this invention are used to administer an intra-articularfluid-filled space injection. In both embodiments, the injection fluidcontains, for example, an anesthetic and the end is adapted forinsertion into the epidural or intra-articular fluid-filled tissuespace. It is contemplated that either the pharmaceutical-containing or apharmaceutical-free (testing) fluid is used to identify the fluid-filledtissue space during the needle placement phase of the procedure.Suitable pharmaceutical-free fluids include, for example, physiologicalsaline, phosphate-buffered saline, artificial cerebral spinal fluid,Ringers, 5% dextrose, or filtered air. Once the fluid-filled tissuespace is identified using the pressure difference method, the injectionfluid is changed (i.e., requiring a plurality of fluid reservoirs) to apharmaceutical-containing fluid. The use of a pharmaceutical-free fluidduring the needle placement phase minimizes or eliminates the deliveryof the pharmaceutical to non-target tissues.

Frequently, procedures that require an epidural injection of anestheticare lengthy and, in addition to the initial (loading) dose, one or moresubsequent (maintenance) doses are required. Typically, an indwellingcatheter is used to administer the plurality of doses. In anotherembodiment, the invention provides a method for administering anepidural injection requiring a plurality of injections wherein, duringadministration of the second (and subsequent) doses, the pressure of thefluid at an interface between the end and the tissue of said patient iscalculated, and the flow rate of the injection fluid during said secondinjection is controlled such that the pressure does not exceed thepre-set maximum pressure. Likewise, this technique may be used forindwelling catheter maintenance (i.e., to determine whether the catheterremains in a target tissue such as the epidural tissue space) whether ornot an additional injection is contemplated or desired at that time.

It is further contemplated that this injection device may be used foraspiration of a fluid-filled tissue space after the identification of afluid-filled space is determined. Aspiration may be used either towithdraw a sample of tissue or extracellular fluid (i.e., cerebralspinal fluid, intra-articular fluid, blood, etc.), or may be used todetermine the correct placement of the injection needle. During anaspiration procedure, the “entry pressure” is measured in the samemanner as the pressure within the fluid-filled tissue space, which ischaracterized by a loss of pressure. Likewise, false loss of pressure isalso identified using an aspiration procedure because the internaltissue structure (i.e., cyst) will be quickly drained of its contentsand the entry pressure will rise above the threshold entry pressure.

The motor, the coupling associated with the motor and the electroniccontroller discussed below are at least partially disposed within theapparatus housing for protection.

The fluid storage device is filled and a setup process is initiatedduring which the clinician places a preloaded syringe into the syringereceptacle on the top of the instrument. The clinician can change thefluid flow rate and peak pressure to be dispensed. Then they operate atouch-screen activation and/or pneumatic control such as a foot pedaland initiate the fluid flow. Alternatively, commands may be initiated bythe clinician either electronically or by voice commands. Duringdispensing, the output from the transducer is used to calculate thecurrent fluid pressure. If this pressure approaches a certain threshold,the fluid flow rate is automatically stopped to prevent excessiveinjection of drugs into the non-targeted tissues, thereby ensuring thatthe patient does not suffer undue pain or damaged to tissues from excessfluid-flow. Several optional features are also provided includingaspiration, purging or charging the media with or without air.

Throughout the process, the clinician is provided with constant currentinformation on the ongoing process, both visual and aurally, includingthe current flow rate, total volume ejected or aspired, tissuepressures, entry pressures and other parameters. The slavemicroprocessor receives commands from the master microprocessor andgenerates the drive signals required to operate the motor.

In another embodiment it is possible to have two distinct drives toallow the placement of multiple syringes onto a single device. In suchembodiment presented herein, a first drive is used with a separatesyringe, tubing set and needle for the delivery of a first drug and asecond drive contains a separate syringe, pressure transducer, tubingset and needle for a second drug. Each drive is capable of the featuresdescribed above. In addition, one of the two drives may also be usedwithout the capacity to sense pressure and be entirely used to deliverya drug at a specific flow-rate. This drive may be used to delivery alocal anesthetic prior to the use of the second drive in which apre-determining pressure limiting feature is used to identify afluid-filled tissue space.

Since the benefits of limiting drug infusion into the non-targetedconnective tissue region of a patient have been described, there is aneed at times to provide adequate local anesthetics and other drugs tothese tissues without limiting the ability to inject a therapeutic drugsuch as local anesthetic for the purpose of producing superficialsoft-tissue anesthesia prior to attempting to identify a fluid-filledtissue space such as the epidural or intra-articular or otherfluid-filled spaces of the body. Hence, an instrument with two drivesachieves these objectives.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a view of an authorized disposables assembly of the invention;

FIG. 1A is a view of one embodiment of a proprietary connector of theinvention;

FIG. 1B is a view of second embodiment of the proprietary connector ofthe invention;

FIG. 2 is a top view of a computer-controlled drug delivery unit housingwith a disposables assembly in place for use;

FIG. 3 is a view similar to FIG. 2 of the unit without the disposablesassembly;

FIG. 4 is a schematic representation of a different embodiment of thecomputer-controlled drug delivery system of the invention;

FIG. 5A is an enlarge view of the plunger stage and top end of a syringeplunger of the invention;

FIG. 5B is an enlarge view similar to FIG. 5A of the stage approaching athumb pad or thumb flange of the syringe;

FIG. 5C is an enlarge view similar to FIG. 5A of hooks or catches of thestage engage to the thumb pad of the syringe;

FIG. 5D is an enlarge view similar to FIG. 5A of the stage reversingdirection and showing the hooks pull back on the thump pad;

FIG. 6 is a partial view of the drive unit and its side-panel;

FIG. 7 shown the disposable components connected assembled and theID-Connector inserted into the side of the drive unit transferringinformation to/from a CPU in the drive unit;

FIGS. 8A to 8G are different screen shots of the touch screen of thedrive unit during various phases of operation of the invention;

FIG. 9 is a schematic, sectional view through the area of the spine of asubject for an epidural injection, showing the tissues through which aneedle will travel, correlated to pressure setting according to theinvention; and

FIG. 10 is a partial exploded view of parts of a disposables assemblywith tubing and needle, and further with an elongated handle forconnection between the tubing and needle for improving control anddexterity for any type of injection, but in particular useful forimproving inferior alveolar injections.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, in which like reference numerals are usedto refer to the same or similar elements, FIG. 1 shows as disposablesassembly 10, made up of various parts that are permanently connected toeach other and are supplied in sterile package for single use inconjunction with a computer-controlled drug delivery instrument or driveunit 50 shown in FIGS. 2 and 3, which together form a systemschematically shown in FIG. 4.

The subject invention pertains to a system for determining location anddelivering drugs in fluid-filled tissues such as the epidural space,intra-articular space, globe of the eye, cysts, vessels and otherfluid-filled spaces of the body. The injection of such drugs, such as,but not limited to local anesthetic solutions as, cortico-steroids,hydroxyapatite, joint replenishment drugs, sclerosing agents and otherdrugs are typically injected into a fluid-filled tissue space fortherapeutic purposes. Importantly, due to a variety of factors, injectedfluid disperses through a tissue at different rates, causing the fluidpressure to vary. The present inventor has discovered that this pressure(or an internal pressure related to the resistance pressure of a tissue)is indicative of, and may be used to identify several types of tissues.

The present invention provides a method and device that enables thepractitioner to accurately identify fluid-filled tissue space whilelimiting the placement of drugs into non-targeted tissues. This isperformed for a diagnostic and therapeutic procedure. The current deviceutilizes the pressure of a fluid from a needle or catheter (“theinjector”) following placement of the needle/catheter within the tissuein order to properly identify the accuracy of placement and to monitorthe (correct) placement during an injection or aspiration. Specifically,the present device utilizes a pre-determined first pressure to preventthe flow of a drug within a non-targeted (first) tissue site and toresume a flow of fluid once a pressure either drops below apre-determined same pressure. In an additional embodiment the device mayutilize a first pre-determined first pressure to prevent flow of thedrug and a second different pre-determine pressure to which the pressuremust enter to allow flow to resume. Utilizing a pre-determined pressureto allow the accurate needle/catheter placement throughout theinsertion, injection, and maintenance phases of the procedure. First,the pressure is used during the needle/catheter insertion to identifythe anatomical structures and to enable the clinician to correctlydetermine when the lumen of the injector is placed within thefluid-filled tissue space. Hence, a non-continuous fluid flow of drug isused to identify the intended target tissue.

The pre-determined pressure is also used to prevent flow of the drug ata specified value and then allows fluid-flow to resume once apre-determined pressure value is below said value. This may be usedduring the maintenance phase of the procedure to ensure that theinjector remains within the intended tissues such as the epidural tissuespace. There is a particular risk during medical procedures that requirean initial epidural injection (i.e., loading dose) followed by periodicmaintenance doses in order to maintain the desired level of anesthesia.Typically, an indwelling catheter is inserted into the epidural spaceand remains attached to the injection device throughout the procedure.Frequently, the patient is moved between the loading dose and one ormore of the maintenance doses. Such movement may cause a correctlyplaced catheter to migrate from the epidural tissue space into anon-target tissue. The present device monitors the pressure during allperiodic doses (i.e., the loading dose and all subsequent maintenancedoses). Thus, drug will not be injected into tissues that are unintendedand non-therapeutic to the patient. Additionally, the clinician isalerted should the catheter migrate during the maintenance phase. Thecurrent device utilizes non-continuous fluid-flow and pre-determinedpressures to properly identify the accurate placement of an indwellingcatheter while limiting the flow of drug into non-targeted tissues.

Thus, the advantages of the present device over the prior art include(i) a means to identify the fluid filled tissue space such as theepidural, intra-articular, globe of the eye, cysts and blood or otherfluid vessels, but not limited to these structures, while utilizing anegligible volume of drug-containing solution, (ii) a means to identifynon-targeted tissues by limiting the flow of drug from a firstpre-determined pressure limit. (iv) a means to monitor the placement ofa needle/catheter for the entire duration of catheterization (i.e.,during the maintenance phase of drug infusion) by monitoring the flow ofdrug into a fluid-filled space.

According to the principles of this disclosure, the pressure is measuredusing the pressure/force of a fluid injected/infused from acomputer-controlled drug delivery system capable of detecting pressureresistance during infusion. The pressure resistance measure is convertedinto a visual as well as audible signal on a continuous basis while thefluid flow of drug is non-continuous. The computer-controlled drugdelivery system is continuously modulated based on the pressuregenerated producing a non-continuous fluid flow. Thus, the flow-rate isvariable and is dependent on the pressure of the system. It iscontemplated that the pressure is the primary controlling variable ofthe system.

The flow-rate, therefore, becomes a secondary variable that is modulatedwithin a pre-determined range in order to maintain the desiredfluid-flow. In one specific embodiment, the fluid flow is stopped atpressures exceeding a pre-determined threshold (maximum pressure). Theflow-rate, as a secondary variable, may be limited so that fluidinjections are not unduly rapid under low pressure conditions. It iscontemplated that the relationship between pressure and fluid flow ratemay either be binary or continuous. A binary relationship exists whenthe injection device is configured to deliver a fluid at a single,pre-determined flow rate for any pressure less than the pre-set maximum.Thus, the fluid flow is either on or off based on whether or not thepressure exceeds the threshold. Alternatively, the flow rate may bemodulated by as a function of pressure. In this case, flow rate will bereduced as the maximum pressure is approached and increased as thepressure drops. Optionally, the flow rate may be limited to a firstpre-set maximum pressure and a flow rate resumes at a second distinctpre-determined pressure.

It is also contemplated that the injection device optionally may containa means for recording and/or displaying relevant injection dataincluding, for example, instantaneous flow rates, pressures, andinjection amounts. All measurements and information may be presented tothe clinician in “real-time” so that the clinician may determine whetherthe injection is being delivered to the intended location and/or correcttissues and may modify the injection technique accordingly. In addition,the measurements may be recorded for later review and documentation ofthe clinical event.

It is also contemplated that multiple syringes driven by separatesyringe plungers may be used to allow multiple drugs to be injected aswell as a second syringe drive that does not required a pre-determinedpressure to be reached for any said purpose. The second drive can beprogrammed on a specific flow-rate to allow infusion of a drug such aslocal anesthetic and other therapeutic drugs into a variety of tissues.

In yet another embodiment the device may contain two distinct syringedrives in which both are capable of modulation based on fluid-pressureas previously herein described.

Authorized Disposables Assembly

The invention includes a new design of a disposables assembly ordisposable assembly, made up of syringe, pressure-transducer, tubing setand needle plus one of a variety of unique proprietary connectionadaptors (disclosed herein is called an “ID-Connector” or abbreviated as“ID-Connector”) to be affixed as part of the disposable assembly used inconjunction with a computer-controlled drug delivery system. FIG. 1illustrates one embodiment of the disposable assembly of the invention.

The computer-controlled drug delivery system of the invention,illustrated in FIGS. 2, 3 and 4, provides numerous benefits to patientsby providing a more accurate injection. The invention also providesnumerous clinical benefits for practitioners by producing superioroutcomes. Instruments embodying the invention are shown to provide amore precise and safer administration of drugs for a variety ofapplication such as epidurals, interacticular and other subcutaneousinjections. Ensuring the use of only authorized disposables componentsis critical to the proper performance of such instruments. The selectionof incorrect components could lead to a number of undesirable outcomesincluding:

1. Incorrect volumes administered.

2. Improper flow-rate and pressure measurements.

3. Use of non-fitting components leading to error.

4. Use of poorly designed non-authorized substitute components.

To ensure that the appropriate disposable components are used with thecomputer-controlled drug delivery system of the invention a proprietaryconnector 12 in FIG. 1 is included. Connector 12 has first and secondmating parts 14 and 16 and has the ability to provide a uniqueconnection and/or electrical circuit connection and/or required datainformation transfer prior to use. Connector 12 acts as a controllingelement between the disposables assembly parts 10, made up of syringe18, pressure-transducer 20, tubing set 22 and needle 24, and theassembly is connected to the computer-controlled drug deliveryinstrument 50 of FIG. 2, by a jack 30.

Currently there are no structural means to provide verification of theselection of disposable components used with a computer-controlled drugdelivery instrument.

The proprietary adaptor connection 12 of the invention ensures that onlyauthorized, correctly configured, correctly sized and sterilizeddisposables assemblies 10 are used with the instrument. This isaccomplished in the following structural implementations.

The connection 12, electronically connects the in-line, electronicpressure transducer 20 to the computer-controlled drug deliveryinstrument 50, using an external data cable 21 from transducer 20 to thefirst mating part 14, that is plugged to the second mating part 16, andis connected by a second cable 23 and the jack 30 that is plugged intothe instrument 50. The pressure-transducer 20 is connected inline, thatis, immediately between the end 19 of the cylinder of syringe 18, andone end 25 of tubing 22, e.g. by Luer connections that have beenpermanently bonded as explained below, so that the instantaneous, actualfluid pressure in the drug delivery line is being sensed and used by theinstrument, which provides a close approximation to the actual,instantaneous fluid pressure at the point or tip of the needle 24, andtherefore, at the location in the patient's body where the tip islocated.

The electronic pressure-transducer or sensor 20 provides pressure datavia the electronic data cable and connector 21-12-23, that is connecteddirectly to the unit 50 to collect such pressure measurements. Byincorporating the intervening proprietary connection 12 between theelectronic pressure-transducer 20 and the computer-controlled drugdelivery instrument 50, a verification and/or authorization check-pointcan be established. The proprietary connection 12 is used to identifyand verify the connected components. The disposable components 10 areprovided as an authorized single-use, bonded disposable set in which allcomponents are glued together, i.e. the syringe 18 is permanently bondedto the tubing-set 22 with electronic pressure sensor or transducer 20permanently bonded there between, up to the first mating part 14, allbeing permanently bonded to each other. This disposables assembly 10 isused and discarded as a unit. It is further connected to the drive unit50 by the second mating part 16 that can only be connected to theproprietary first mating part 14 to ensure that only authorizeddisposables assemblies 10 are used and that they are only used once.

The electronic pressure transducer 20 can, for example be any one ofvarious piezoelectric pressure sensors available from Merit MedicalSystems, Inc. such as the Meritrans® Pressure Transducer item MER212.

The proprietary connection 12 disclosed herein is called an“ID-Connector.” The ID-Connector 12 is composed of two components, onebeing the ID-Connector-Plug 14 and the Custom-ID-Connector-Receptacle16. Since the role of “plug” and “receptacle” can be reversed or eachcan even have both plug and receptacle features, they are also calledfirst and second mating parts 14 and 16 in this disclosure.

The ID-Connector system 12 is designed as an electronic physical bridgebetween the instrument 50 and an authorized, bonded-together, disposableset-up or disposables assembly 10. The ID-Connector-Plug 14 has twoopposing functional sides 14 a and 14 b as shown in FIG. 1A, that areplugged into, and permanently bonded with each other. One side 14 a isthe conventional plug or socket that allows the connection of a standardcomponent such as that from the existing electronic pressure-transducer(i.e. a Meritrans Pressure Transducer item MER212) of disposablecomponents. The opposite side 14 b of the ID-Connector 14 is a customID-Connector-Plug side and has one end that is conventional and plugsinto side 14 a, and an opposite proprietary side. As mentioned, sides 14a and 14 b are also bonded to each. The Custom-ID-Connector-Plug side 14b connects via its proprietary mating face, i.e., a custom set ofprojections and depletions 14 c, to the second component or theID-Connector Receptacle 16 via its proprietary mating face, i.e., acomplementary set of projections and depletions 16 a. This connection of14 c to 16 a is detachable so that replacement disposable set-ups 10 canbe used. Part 16 is connected to the drive unit 50 via electronic cable23 and jack 30 as shown in FIGS. 1 and 2. The ID-Connector system orconnector 12 is designed in a variety of unique configurations toinclude additional connection socket/pin combinations as shown in FIG.1B for a proprietary connection that will provide a unique “signature”to the system, thus providing verification prior to operation.

As illustrated in FIG. 1, another authorization scheme of the inventionincludes a computer chip, SIM or other uniquely coded circuit 14 d thatis also electrically connected to the drive unit 50 by the cable 23 whenparts 14 and 16 are mated, and which is read by an authorization programor circuit in unit 50. If the coded circuit 14 d is genuine, the unit 50will operate properly, if not, the unit is disabled and a warning suchare “Unauthorized Syringe Detected” is posted on the screen of the unitand optionally a warning sound is made, including but not limited to avocalization of words, an alarm, or other warning signal or anycombination thereof. The coded circuit 14 d is also coded for a one-usefunction whereby the authorization program or circuit in unit 50 willdetect if a specific disposable set-up 10 was previously used and, ifso, again disable the unit 50 and post a warning. The coded circuit 14 dcan also be coded with the physical (e.g. tubing, needle and syringegauge) and chemical (e.g. syringe contents) attributes of the disposableassembly 10 that are also read by the circuit or program in unit 50. Thecoded circuit will then, set, over-ride or modify any settings that aremanually programmed into the unit 50, taking into account the attributesof the disposable assembly to insure proper and safe functioning of theunit.

The coding circuit 14 d can also be used with or without the mechanicalproprietary features of FIGS. 1A and 1B, although using both willincrease security. In any case, failure to recognize a properconnection, be it physical, electrical or digital, prevents theoperation of the instrument 50.

The invention thus contemplates a new pin connection of the ID-Connectorsystem 12 to complete a required circuit so that the instrument willfunction to verify, validate and read information from the properdisposables set-up that has been selected for the instrument. Theelectronic connection in the ID-Connector system provides digitalinformation via stored memory within the circuit 14 d of the connectorelement 12. The new pin connection of the ID-Connector can also providea unique key/lock interface connection and thereby validating thecomponents to be used in conjunction with the instrument 50.

One or more of any of these above-described security measures can beutilized either solely or in any combination. The unique ID-Connectorsystem 12 is positioned between the current electronicpressure-transducer 20 and the drive unit 50, but it is anticipated thatthe ID-Connector system could be bonded, glued or connected to othercomponents to be used with this instrument such as the syringeexclusively or the tubing set exclusively. In the preferred embodimentthe ID-Connector fits between these two connections, however, it isanticipated that this ID-Connector system could be connected at avariety of different interface locations and retain the functionintended for verification and identification of the unique disposableset-up.

The attachment 12 performs as follows:

the ID-Connector system is manually attached at the interface junctionin a variety of different modalities; and

in a preferred embodiment the ID-Connector system is part of a completedisposables set-up 10 that comprises syringe, pressure transducer,tubing set and needle.

In the preferred embodiment the permanent attachment of the needle maybe optional so that a practitioner may selection a preferred needle fora particular purpose. The components are assembled individually or as inthe preferred embodiment they are glued (i.e. bonded) together andprovided as a single disposable set-up ensuring that the properdisposable components were selected.

The preferred embodiment is a bonded-ID-Connector disposable setup. Itis anticipated that a variety of configurations could be used inconjunction with the instrument 50. These consist of different sizecomponents, i.e. needle, syringe, tubing-set and pressure transducers.The integration of a ID-Connector system ensures the authorized set-upand also possesses the ability to interact with the instrument 50 toconfirm and identify the disposable set-up to be used. This representsan important verification to the system. It ensures use of appropriatecomponents and/or drugs. It is anticipated that a pre-filled syringe 18with a drug could be supplied with the ID-Connector system 12 anddisposables set-up 10, or the syringe can be supplied empty so that itcan be filled onsite with a desired drug, saline or other fluid. Forpre-filed syringes 18, the ID-Connector 12 (in its chip 14 d) containsthe information related to that drug contained within the syringe andpresented for use in the instrument.

Improvements over the prior art include an ID-Connector to ensure thatthe proper selection drug delivery components are utilized with acomputer-controlled drug delivery system. The ID-Connector systemfurther resolves multiple deficiencies of a disposable injection system.Importantly, it will not change the workflow practice during the set-upof the instrument while ensuring the use of this novel component. TheID-Connector system does not add additional steps while providingverification of authenticity of components to be used with the overallsystem and the like. The use of the ID-Connector system also leads to acost savings when ensuring verification.

FIG. 10 illustrates parts of a disposables assembly of anotherembodiment of the invention, namely tubing 22 with end 25 to bepermanently fixed to an in-line pressure sensor not shown in FIG. 10.This embodiment includes a rigid, plastic, sterile handle 27 fixed tothe opposite end of the tubing 22 and having a male luer lock that is tobe detachably connected to a needle 24 of choice for a particular typeof injection into a selected anatomic site. The elongated handle 27 ofthis embodiment increases manual control and dexterity in placing theneedle, in particular because of rotational control. This isparticularly important for IA-injections (i.e., inferior alveolarinjections), but will enhance epidural and other types of injections aswell.

The elongated handle 27 is advantageously about 15 cm long (about 6inches), or in the preferred range of about 10 to 20 cm long, withtubing 22 of about 122 cm long (about 48 inches).

Pressure-Controlled Injection Device

As described above, the injection device that is exemplified by thedrive unit 50 in FIGS. 2, 3 and 4, uses a non-continuous fluid-flow bycontinuously monitoring a pressure using the electronicpressure-transducer 20, that is preferably the pressure of the fluidduring injection. Based on a pre-determined pressure that is set by thepractitioner and stored in a memory 80 of a microprocessor or computer82 of the electronics in unit 50, fluid-flow will stop, and based on apre-determined pressure fluid-flow, will resume. It is possible that thesame pre-determined pressure is used for both of these settings. In suchcase the pressure will build as fluid initially enters the tissue to apre-determined level and then stop when the pressure drops below thispre-determined level. Thereafter fluid-flow will resume creating anon-continuous fluid flow.

The invention has defined pre-determined levels of pressure to enablefluid-flow into targeted tissue sites while limiting the flow of drugsinto non-targeted tissues. This enables a clinician to selectivelyinject drugs into specific sites and intended tissues for diagnostic andtherapeutic procedures. Preselected maximum allowable pressure limitsand/or flow rates are stored in memory 80 and define either the maximumrecommended pressures that patients usually tolerate, or other criteria.As the pressure approaches this limit, a visual and/or audible alarm isgenerated for the clinician, i.e. on screen 62 and via speaker 84 thatis activated by data from the microprocessor 82. In addition, datadescriptive of the whole injection process is stored for future analysisin memory 80, as discussed above.

Method for Administering Injections into a Fluid-Filled Space

An exemplary method for administering an epidural injection follows.These principles and methods may be easily adapted for injections intotissues and anatomical areas other than the epidural space.

The first pre-determined upper pressure limit is determined by theclinician. Typically, the first pre-determined upper pressure limit isnot greater than 200 mm/Hg. It is contemplated that using such a settingthe injection system will administer a negligible amount of medicationinto the connective tissues and a then by selecting a secondpredetermined pressure below 50 mm/Hg at which the fluid flow willresume. Hence the needle is properly positioned within the fluid-filledspace of epidural tissue-space because the pressure within the epiduraltissue space is believed to be between about +15 mm/Hg and −15 mm/Hg,whereas the pressure associated with the Ligamentum Flavum is above 200mm/Hg.

The known pressure measurements within the extra-ligamentary tissues aretypically about 100-200 mm/Hg. With the injection device 50 having asecond pre-determined pressure at which the fluid flow will resume, thatis 50 mm/Hg or below, there will be no significant fluid flow once theneedle enters the subcutaneous tissues as the pressure will quickly riseand be maintained as long as the needle resides within the subcutaneoustissues (extra-ligamentary tissues). The clinician, followingtraditional epidural injection technique, will advance the Touhly needleand encounter the ligamentum flavum. Still no fluid flow will occurbecause, as noted above, the ligamentum flavum generates a pressuregreater than 100 mm/Hg. Upon penetrating the ligamentum flavum (i.e.,needle entry into the epidural fluid-filled space) the pressure willimmediate drop below 50 mm/Hg triggering an optional visual displayand/or audible tone and/or spoken word such as “Located Epidural,” andthe drug-containing fluid will begin to flow into the intended targetsite. Thus a non-continuous fluid-flow is utilized to identify thetargeted tissues. It is possible that the first and secondpre-determined pressure values are set to the same number to allow fluidflow to occur only after the pressure drops below a pre-determinedpressure.

The pressure sensor 20 or plural sensors of the injection device 50provide an automatic safety feature in the event that the injectionneedle leaves the epidural tissue space (e.g., from clinician error orpatient movement) or its patency is compromised. If the needle 24 leavesthe epidural tissue-space, either by withdrawing through the ligamentumflavum or by contacting the dura, the pressure will immediately rise toa first selected pressure P1, causing a slowing and eventual stoppage offluid flow at fluid pressures>200 mm/Hg. This has been shown to occurwithin approximately 2 seconds time (see, Ghelber-Regional Anesthesiaand Pain Medicine Vol 33 No 4 2008, page 349 FIG. 2). Optionally, thischange in pressure from <50 mm/Hg to >200 mm/Hg will again trigger avisual and/or audible alarm to alert the clinician of improper needleplacement. Flow will again automatically resume once the needle isreestablished in the epidural tissue space and the instantaneouspressure at the needle point drops below P1, or, in a further embodimentof the invention, when the pressure drops to a second selection pressureP2 of equal to or below 50 mm/Hg. This automatic safety feature of theinjection device helps prevent injection of the anesthetic solution intothe spinal cord.

Turning to FIG. 9, the area of the spine of a subject for an epiduralinjection is shown. Starting from the outside injection site for thepoint of the needle 24 at the left in FIG. 9, the tissues in this areainclude various layers of skin, fat and connective tissue 110, followedby the epidural space 112, that is the anatomic space of interest in apreferred embodiment of the invention. Beyond the epidural space 112 isthe dura mater 114 of the spinal cord 116. Clearly it is important thatthe right-ward progress of the point of the needle 24 through thetissues, stop before reaching the spinal cord and this achieved by theinvention. Cross sections of the bones of the backbone in this area arealso shown.

According to the invention the microprocessor 82 and memory 80 areprogrammed with the first pressure P1, of, for example, about 200 mm/Hg,that is selected to be equal to or greater than the instantaneous fluidpressure at the point of the needle as it enters and moves through thetissue 110. At or above this pressure P1, the motor 96 is stopped andthe fluid flow to the needle point stops. When the needle point entersthe epidural space 112, the instantaneous fluid pressure drops to belowP1 and the microprocessor causes the motor to start again to resumefluid flow, now into the epidural space 112 according to one embodimentof the invention. According to a second embodiment of the invention, thesecond selected pressure P2 stored in memory 80 must be reached beforefluid flow resumes. In a third embodiment of the invention, when a thirdselected pressure P3 stored in memory 80, that is greater than P2 butless than P1, is reached, the fluid flow will stop again. Reaching thisthird pressure P3 indicates that the needle point has pressed into thedura 114 or is otherwise leaving the anatomic target space. The spacesor layers through which the needle point will travel are correlated tothe pressure settings P1, P2 and P3 according to the invention, in FIG.9.

The first selected pressure P1 for stopping fluid flow is preferableabout 200 mm/Hg for an epidural injection, but can be in the range ofabout 25 to about 300 mm/Hg depending on the tissue to be firstpunctured by the needle point. Pressure P2 for resuming fluid flow ispreferably about 50 mm/Hg for an epidural injection, but can be in therange of about 20 to about 150 mm/Hg depending on the anatomic space ofinterest. The third selected pressure P3 for stopping fluid flow again,is preferable about 125 mm/Hg for an epidural injection but can be inthe range of about 80 to about 180 mm/Hg depending the anatomic space ofinterest. The use of three set pressure improves the flow/no-flowcontrol as the needle point moves through different tissue types for anyfluid-filled anatomic space capable of receiving fluid at a lowerpressure than tissues surrounding the anatomic space.

A feature of the present injection device and accompanying method is theability to quickly and accurately identify a “false-loss-of-resistance”or “false-positive” (typically within 2-4 seconds). Afalse-loss-of-resistance typically occurs when a traditionalloss-of-resistance manual syringe technique is used and a drop ofresistance occurs when the epidural needle enters a cyst or less densespace outside the epidural tissue-space. The ligaments in the area areunderstood to be less dense and a false loss of resistance is notuncommon. Many times the subjective nature of this anatomic location canlead the clinician to believe he has located the epidural tissue-space.When using the computer-controlled drug delivery system with pressurecontrol, once the needle enters such a space it quickly fills the spaceor pressurizes the less dense tissue with fluid and the recordedpressure rises above 200 mm/Hg and objectively indicates a“false-loss-of-resistance.” This would typically not be the situationusing a traditional manual syringe technique or a system that has acontinuous fluid flow of drug from a syringe pump. In such cases oncethe initial loss-of-resistance is encountered, the syringe is moved andthe operator delivers the bolus of the fluid (no longer subjectivelytesting for a “loss-of-resistance”) thereby depositing anestheticsolution in an anatomic location outside the intended epiduraltissue-space (again see, Ghelber-Regional Anesthesia and Pain MedicineVol 33 No 4 2008, page 350, FIG. 3 is a line graph demonstrating afalse-loss-of-resistance at time of about 250 sec.). This observation ismost likely associated with ligamentous tissue, measured during theadministration of an epidural injection. The incorrect tissue structurewas quickly pressurized, returning the measured fluid pressure>200mm/Hg. Insertion of the catheter into the epidural space and subsequentfluid injection does not result in a significant and rapid rise inpressure, indicating that the catheter is correctly located.

It is contemplated that a pharmaceutical-free fluid is used to identifythe epidural tissue space during the needle placement phase of theepidural procedure. Suitable pharmaceutical-free fluids include, forexample, sterile saline, artificial cerebral spinal fluid, Ringers, 5%dextrose, or filtered air. Once the epidural tissue space is identifiedusing the pressure differential, the injection fluid is changed to apharmaceutical-containing fluid. The use of a pharmaceutical-free fluidduring the needle placement phase minimizes or eliminates the deliveryof the pharmaceutical to non-target tissues.

Another feature of the current device and methodology is the objectivenature of pressure measured by a computer-controlled drug deliverydevice that is monitored during all phases of the injection process. Theclinician, therefore, no longer relies on the subjective nature of a“feel” but rather is provided with objective information of absolutevalues while performing each phase of this critical technique. Eachphase of the technique is improved by the ability to continuouslymonitor the pressure while using a non-continuous fluid-flow of drugallowing adjustments to be made that ensure greater safety and efficacyof the injection.

In another example, the clinician may reset the pre-determined maximumallowable pressure once the fluid-filled space is penetrated and theinjection has begun. As noted above, prior to needle entry into theepidural space, the fluid pressure is greater than 200 mm/Hg so littleor no fluid is being delivered. Upon entry of the fluid-filled space thepressure drops below zero and gradually rises to about 1-10 mm/Hg. Thisdrop in pressure initiates the flow of fluid from the injection device.At this time, the maximum pre-set pressure value may be changed to anew, lower, maximum. For example, the pre-determined maximum pressure inwhich fluid flow stops may be reduced to 25 mm/Hg which will provide anextra level of patient safety in the event that the injection needlecontacts the dura mater or is withdrawn from the epidural space. The newpre-determined lower maximum pressure will cause the fluid flow to bearrested sooner, and at lower ectopic injection amounts, than theoriginal pre-set value. The change in pre-determined maximum pressurestop of fluid flow may be performed manually by the clinician orautomatically by a control element in the injection device.

It should be understood that the example of 200 mm/Hg as thepre-determined maximum pre-set pressure for stoppage of fluid flow is anexample and that either a lower or higher pre-set pressure may beselected at the discretion of the clinician. Also, the secondpre-determined 50 mm/Hg pressure value at which fluid flow resumes is anexample and that either a lower or higher pre-set pressure may beselected at the discretion of the clinician and is merely illustrative.The principles and techniques may be modified for an injection intoalmost any anatomical location. What is of particular importance in thisembodiment of the method and device is the ability to define and selectpre-determined values of pressure to produce a non-continuous flow ofdrug for diagnostic and therapeutic administration.

The techniques described herein are equally applicable to human andanimal tissues.

Non-Continuous Fluid-Flow with One or More Distinct Pressure LimitsCombined with an Auto-Detect-Fluid Aspiration

In preparation for using the unit 50, and with reference to FIGS. 1, 2and 3, a disposables assembly 10 of FIG. 1 is removed from its sterilepackaging and the pre-filled body of syringe 18 is pressed into asemi-cylindrical syringe cradle 52 defined in the upper surface of thehousing of unit 50 as shown in FIGS. 2 and 3. The syringe body 18 isheld firmly in place in cradle 52 by a pair of spring-loaded clamps 54and is kept from moving axially in the cradle 52 by having its fingerflange 90, that extends for the top end of syringe 18, engaged within acorrespondingly shaped finger flange recess 55. The plunger 70 ofsyringe 18, that is in its fully extended, syringe-full location shownin FIG. 2, is received in a plunger recess 56 in the upper surface ofthe unit housing, and is sized amply long, wide and deep to contain andsuspend the plunger 70 without contacting it so the plunger can bepressed into the syringe body without obstruction.

A movable stage 58 with three spring-loaded thumb flange catches orhooks 60 that are pivotally mounted to the stage 58, is movable undercomputer control along the plunger recess 56. As will be explained morefully below, the stage 58 is moved to the right in FIGS. 2 and 3, untilthe stage 58 is close enough to a thumb flange 72 of syringe 18, toallow facing beveled surfaces of the three hooks 60 to engage the thumbflange 72 form the bottom and its opposite sides, to spread under thecontinued movement of stage 58, and then snap closed below the thumbflange 72. A sensor in unit 50 then senses resistance to the furthermovement of stage 58, and the stage stops. Since, at this point, theplunger 70 is effectively axially fixed to the stage 58 by theengagement of the catches 60 on thumb flange 72, any further rightwardto leftward movement of the stage 58 will also move the plunger 70 tothe right, i.e. to expel fluid form the syringe body, or to the left toaspirate fluid back to the syringe body.

The pressure sensor 20 of the assembly 10 is plugged to the proprietaryconnector 12 and connector 12 is plugged to the unit 50 via jack 30.

As mentioned, the invention relates to a tissue site location andinfusion system utilizing a non-continuous fluid flow with one or more(or—“more then one”) pressure limits and auto-detect-aspiration system.

The system is composed of the drive unit 50 and the disposable set-upcomponents 10. The drive unit 50 houses the microprocessor or CPU 82,electronic circuitry board 92, a power supply 94 and electronic motor ormotors 96 (since in the embodiment of FIG. 4, two syringes can beaccommodated). Each electronic motor 96 rotates a spiral shaft 98 thatmoves a syringe armature 100 in a forward and reverse direction. Thesyringe armature 100 contains a load cell sensor to detect force.Armature 100 is connected to the stage 58 to move the stage in eitherdirection. As also mentioned, the disposable set-up 10 comprises the newIdentification-Connection component 12, syringe 18, in-line pressuretransducer 20, tubing set 22 and needle 24.

Detailed Description of Operational Sequence

The top view of the instrument shows the recessed cavity 52 and recess56, together called the syringe cradle, which allows the properpositioning to receive a standard 20 cc syringe 18. Contained within theplunger recess 56 is the movable armature 100 and stage 58 that engagesthe thumb pad or flange 72 of the disposable syringe 18. The mechanismthat engages the thumb pad of the syringe has the series of springloaded hook 60 shown enlarged in FIG. 5A, which automatically capturethe syringe thumb pad.

As shown in FIG. 5B, as the thumb pad 72 is engaged, the spring loadedhooks 60 will move outward, over and then engage the thumb pad inhook-like fashion. This action will secure the thumb pad as shown inFIG. 5C, allowing the syringe stage 58 to mechanically move the syringeplunger 70 in either direction (reverse being shown in FIG. 5D), thusensuring that aspiration can be performed. Additionally a force sensoris integrated into the design of the syringe armature 100. The syringearmature 100 uses optical and mechanical features to identify theposition of the syringe and can calculate the volume of fluid presentwithin the syringe.

Step 1: The drive unit 50 is turned “On” via a separate side-panel 64shown best in FIG. 6 that includes “On/Off”, “Start/Stop”, “Purge”, and“Aspiration On/Off” buttons and Battery Indictors. The “On/Off” buttonpowers up the drive unit and touch screen interface LCD 62. Turning onpower automatically moves the syringe armature mechanism 100 to be in a“home” position shown in FIG. 3.

In FIG. 3 the syringe armature 100 with moving syringe stage 58 with theauto-engage-aspiration thumb-pad receptacle 52, 56 is connected to themovable syringe armature, located on the top of the drive unit.

The top of the drive unit shows feature design, i.e. a syringe cradle,that is designed with detents or clamps 54 on the surface. These detents54 engage the surface of the barrel of the syringe 18 with an interfaceas the syringe is placed within the syringe cradle to cause a temporarylocking of the syringe into the syringe cradle.

Step 2: The drive unit 50 requires the use of a series of disposablecomponents. As mentioned the disposable set-up 10 of FIG. 1 comprises ofthe following system components.

A syringe 18—the preferred embodiment uses a standard 20 cc syringe fromBecton Dickinson, Inc. The design is not limited to a particular size orvolume syringe. The operator will load the syringe with fluid from anappropriate sterile container, such as a multi-dose drug vial orsingle-use glass ampule. The operator may fully load the syringe orpartially load the syringe as the auto-detection feature determines thevolume of drug that is contained within the syringe.

The preferred embodiment uses the in-line pressure transducer 20—such asthe Meritrans® in-line pressure transducer from Merit Medical, SouthJordan, Utah. It is anticipated that the force sensor in the syringearmature could provide information as to fluid pressure and negate theneed for a secondary pressure sensor.

A subcutaneous hollow-bore needle 24—in the preferred embodiment a Touhyneedle such as the Becton Dickinson 20G×3.5″ Touhy Needle. BectonDickinson, Franklin Lakes, N.J.

Sterile tubing set 22—48″ arterial pressure tubing, such as ICU Medical,Inc. San Clemente, Calif.

Identification-Disposable Connector (ID-Connector) 12—the ID-Connectoris a proprietary component and part of the invention herein described.It verifies that an appropriate syringe, tubing set, in-line pressuresensor and needle as recommended by the manufacturer of the inventionare connected to the drive unit. In the preferred embodiment theID-Connect is permanently affixed to the pressure sensor and tubing-setand provided as a single component. It is also possible that theinvention includes all disposable elements provided in a distinct kit,allowing the operator to connect the ID-Connector to the individualcomponents for use.

The ID-Connector is then connected to the drive unit via a removableconnection plug 30, such as the RJ-11 plug shown in FIG. 1 and FIG. 7.It is anticipated that an electrical connection other then the RJ-11plug can be used. A custom electronic plug may be fabricated.

It is anticipated that the ID-Connector may use any and all other meansof relying and communicating to the CPU of the Drive Unit including butnot limited to InfraRed, WiFi, Blue Tooth or other wireless means.

It is anticipated that the verification of the disposable assembly couldalso be accomplished using labeling to include bar-coding and a bar-codereader or some other optical means of detection.

The ID-Connector communicates to the CPU of the drive unit to provideinformation related to the disposable. In the preferred embodiment theID-Connector limits the number of cycles the drive unit can operate withthe disposable set. This may limit usage based on physical cycling ofthe drive-unit and/or by measured time. Additionally, it prevents re-useof previously used or non-sterile disposables providing patient safety.The ID-Connector also ensures the proper selection of the disposablecomponents. In the preferred embodiment the ID-Connector is rigidlyconnected to as many disposable components as possible, i.e. by glue,heat or chemical bonding to the in-line pressure sensor and tubing set.This is, however, not necessary for the unit to function properly.

It is anticipated that additional information may be encrypted into theID-Connector such as, but not limited to:

Drug information such as Drug Name and Formulation, Drug Manufacturer,Lot Number;

Information related to the disposables assembles;

Information related to expiration of dates for drug;

Information related to sterility of disposable kit; and

Date and time the ID-Connector was used.

In the preferred embodiment a 20 cc syringe 18 is connected to theMeritans pressure transducer 20 with attached ID-Connector and 48″Arterial Pressure Tubing set 22. At the distal end of the tubing set aTouhy (hollow-bore) needle 24 is connected such in the FIGS. 1, 2 and 7.

Step 3: After she syringe 18 is inserted in the Syringe-Receptacle, theoperator will view an initial screen 62 on the Drive Unit 50 stating“Load Syringe and Press Continue”. Touch screen interface 62 allows theoperator to touch the “Continue” button which enables theAuto-Engage-Aspiration-Receptacle to make contact with the syringethumb-pad. See FIG. 8B. The Drive-Unit can detect and confirm that theproper disposables have been inserted into the instrument through aseries of features. The confirming design features include:

1. A unique Identification Detector-Connector (ID-Connector)—that isable to communicate with the CPU confirming that the proper disposableassembly has been selected and attached to the Drive-Unit. If theID-Connector detects an improper selection of disposable assembly or anattempt to Re-Use a disposable assembly, the Drive-Unit will preventfurther operation and display a warning message and/or make a signal.The ID-Connector also can limit the number of cycles performed with agiven disposable set-up. The ID-Connector controls the system andfunctions directly and/or indirectly through the CPU. Information ispassed to/from the connector in both directions and therefore the CPUcan store or alter the content and information on the ID-Connectorduring operation.

2. The Auto-Syringe-Detection feature utilizes retention hooks of theAuto-Engaging-Aspiration-Receptacle to verify that the proper sizesyringe is selected. Confirmation is established by the size of thesyringe thumb pad and the diameter between the hooks of theAuto-Engaging-Aspiration-Receptacle. If the syringe size and receptaclesize are mismatched the hooks cannot engage. The loaded syringe is firstdetected through a load cell contained drive unit syringe-armature.Forward motion of the syringe-armature is automatically stopped onceresistance is detected on the syringe thumb-pad. The syringe-armaturewill then reverse direction after the spring-activated hooks engage thesyringe thumb-pad. In the preferred embodiment, when a smaller diameterthumb-pad is used for a syringe size other than a 20 cc syringe theengaging hooks will not engage and a syringe will not be detected. Awarning message is displayed or signal made and further use of thedrive-unit is prevented. It is anticipated that different dedicatedsyringe sizes could be incorporated into specific designs, for example a10 cc syringe or 5 cc syringe.

The Auto-Syringe-Detection feature also determines the volume of fluidwithin a syringe by an optical and or mechanical sensor. The volume isdisplayed.

Once detection of the syringe is completed and confirmed the system canautomatically purge an appropriate amount of fluid into the tubing setto fully charge the disposable.

3. In the preferred embodiment the Auto-Purge feature is activated afterthe Auto-Syringe-Detection feature. This ensures that the proper syringeis installed in the syringe receptacle. It is possible to change aglobal setting so that Auto-Purge does not occur, in which case amanual-purge option can be used from contacting the touch-screen. It mayalso be possible to by-pass purging altogether. By-passing “Auto-Purge”and “Manual Purge” is an option when a syringe disposable set up is usedmultiple times on the same patient, in which case the tubing set wouldhave already been charged from the first purge cycle performed. See FIG.8A.

On the far right of the touch screen shown in FIG. 8C is a series oftouch-tab's that can be assessed at any time during operation.

1—“Patient” screen: Allows patient/doctor information to be input.

2—“Locate” screen: Active injection screen that shows a visual displayof Flow Rate and of fluid pressure during the injection process therebyenabling the operator to locate the target. P1 and P2 values are notedon the screen as well.

3—“Settings” screen: Allows the flow rate and pressure values, P1 valueand P2 pressure value to be changed. Screen brightness, Audio-SoundVolume to be selected. Additional features include “Calibrate Touch”touch screen sensitivity and Set Date and Time, Auto-Purge On/Off.

4—“Data” screen: Allows review, electronic transfer and printing of datacollected during previous Locate Injection performed.

Patient screen is accessed by touching the “Patient” tab on the right ofthe screen. Note that the operator can switch between any screen duringoperation by simply touching the “tab” on the right of the screen.

Touching the “Patient” tab displays a screen (namely FIG. 8C) while theoperator can input patient and doctor data that will be recorded with atime and date for the patient. See FIG. 8C and FIG. 8D.

Referring to FIG. 8E, a setting screen displays the following useradjustable settings:

1. “Brightness” to allow the screen to be made brighter or darker. Onceselected the screen will default to that value in the future.

2. Audio-Volume adjustment to adjust the sound level during operation.

3. Calibrate Touch to adjust the sensitivity of the touch screen toaccommodate for operators using barriers and/or gloves.

4. Set Date and Time to adjust the date and time.

5. Flow-Rate value to adjust the rate selected.

6. Pressure Limit—P1-value. The P1-value is the pressure at which theflow-rate will stop but continues to record, display and announcereal-time pressure sensing.

7. Pressure Limit—Start—P2-value. The P2-value is the pressure at whichthe flow-rate will resume once reached.

In the preferred embodiment the P1-value and P2-value will be different.The P2-value should be lower then the P2-value, this enables a pressure(P1-value) at which the flow-rate will stop after the pressure attainsthat initial limit. The flow-rate resume once the pressure identifies asecond lower pressure defined as P2-value.

However it is conceivable that the P2-value could also be higher thenthe P1-value, in which case the flow rate will only resume when thepressure increases to a new pressure limit. The operator may select thesame P1-value and P2-value.

FIG. 8F illustrates data screen that displays patient information andphysician information and retains a record of the location and injectionevent. This information can be stored on a removable medium and/ordirectly printed to a printer from the drive unit.

The locate screen provides essential information during the location andinjection process of the procedure and is shown in FIG. 8G.

This is the “Locate” mode active screen is viewed during operation. Thefollowing touch-screen features can be accessed directly from thisscreen:

1. “Start”/“Stop” button to start the flow and stop the flow of fluidmanual.

2. “Tare Pressure” feature: Allows the system to subtract erroneouspressure reading do to altitude or height discrepancies between thepatient and the instrument.

3. “End Treatment” will return the user to the Purge Window to reloadeither a new syringe set up for a new patient or allow a second syringeto be used on the same patient.

4. “Volume Remaining” is viewed as a graphic image of a syringe. As thefluid is expressed the graphic picture changes to reflect the change involume showing in the visual.

5. “Pressure” is provided in mm/Hg in real-time during operation.

6. Flow-rate volume that is being used.

7. Visual Graph displaying the pressure reading in a graph format.

8. Audible Sound reflecting the Pressure and Flow of the fluid.

9. P1, and P2 if used, and P3 is used, are represented on the graph ofthe screen. P2 is noted as a lower pressure limited represented as ahighlighted colored horizontal line on the graph itself.

10. “Print”—the operator can print the data and supporting graph fromthis screen.

11. Time and Date are displayed on the screen.

12. Scrolling Graph—representing the majority of the screen shows avisual representation of the Flow-Rate and Pressure data being recorded.This same information is provided to the user in a Audible tone orsignal so that the operator does not have to necessarily view the screenat all times.

Clinical Rational for a Non-Continuous Fluid-Flow with More Than OneDistinct Pressure Limit Value

It is important to set a distinct first upper pressure limit, defined asthe first selected pressure P1, that is to stop fluid flow. This limitsthe quantity of fluid to be injected during the process ofidentification of the fluid filled tissue space. This is an improvementover the prior art since it prevents continuous flow of fluid intotissues which may have many adverse consequences.

A continuous fluid system was used for the detection of a anatomic fluidfilled space, such as the Epidural Space or Intra-Articular Joint Space,in the patents to Timo Lechner (U.S. Pat. No. 7,922,689) and Tim Patrick(U.S. Pat. No. 8,002,736). For these instruments the operator isrequired to place fluid into tissues on a continuous basis to identifythe tissues via pressure. The deficiency of these patents is that acontinuous flow of fluid is required during the continuous pressuresensing and identification of an anatomic site or structure. Thecontinuous fluid flow can: 1) cause tissue damage by over-pressurizationof tissues; 2) Increase the pressure in the tissue introducing a biasingfactor and error to pressure measurements within the tissues leading tofailure of intended action; 3) Cause unnecessary intra-operative andpost-operative pain; 4) Excessive use of drugs and fluids within thetissue can result in an adverse drug interactions for patients.Therefore, a system that utilizing a non-continuous fluid flow systemcapable of real-time pressure feedback is distinctly different currentinventions represented in the prior art.

Having the ability to set more than one specific pressure valuedistinctly different from P1 provides a means to detect a Low PressureTarget within an anatomic location without introducing additional fluid.This uses fluid-flow as the detection parameter to identify of aspecific anatomic location of the body. It creates a location devicethat uses a fluid-pressurized system with non-continuous fluid flowbased on more than one pressure value limit. This is distinctlydifferent from the CompuFlo technology previously presented in U.S. Pat.No. 7,449,008 Hochman.

While the invention has been described with reference to severalparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles of the invention. Accordingly,the embodiments described in particular should be considered asexemplary, not limiting, with respect to the following claims.

What is claimed is:
 1. An apparatus for administering fluid into afluid-filled anatomic space capable of receiving fluid at a lowerpressure than tissues surrounding the anatomic space, the apparatuscomprising: a disposables assembly comprising: a syringe having a bodyfor containing a fluid to be injected into the anatomic space, thesyringe having a plunger movable in one end of the body for dispensingfluid from an opposite end of the body, tubing permanently connected tothe opposite end of the body, a needle connected to the tubing andhaving a point insertable into a subject and movable through tissuessurrounding the anatomic space, for seeking the anatomic space, and anin-line pressure transducer for generating a signal corresponding to aninstantaneous pressure at the point of the needle; a drive unitmechanically connected to the syringe and electrically connected to thepressure transducer, the drive unit including a controller with acomputer, a memory for storing a first selected pressure (P1) that isselected to be compatible with injecting fluid into the fluid-filledanatomic space, a motor connected to and controlled by the computer, anda syringe armature connected to the motor and mechanically connected tothe syringe for moving the plunder into and out of the body forrespectively injecting and aspirating fluid at the point of the needlefor injecting and aspirating fluid into and out of the subject; and thecomputer being programmed to control the motor to move the plunger for anon-continuous fluid flow into the subject until the first selectedpressure (P1) is detected by the pressure transducer at which time themotor is stops to stop a flow of additional fluid to the subject untilthe instantaneous pressure at the point of the needle drops below thefirst selected pressure, at which time the program resumes operation ofthe motor to resume fluid flow to the subject, so that as the needle ismoved in tissues of the subject surrounding the fluid-filled anatomicspace, fluid flow to the tissues stops at instantaneous pressures abovethe first selected pressure (P1) and resumes when the instantaneouspressure falls below the first selected pressure, to indicate the pointof the needle is in the anatomic space and to then resume injectingfluid into the anatomic space.
 2. The apparatus of claim 1, includingthe memory storing a second selected pressure (P2) that is below thefirst selected pressure (P1) by a first selected amount, the computerbeing programmed to resume operation of the motor to resume moving theplunger to resume flow of fluid to the needle point when theinstantaneous pressure is below the first selected pressure (P1) by thefirst selected amount.
 3. The apparatus of claim 1, including the memorystoring a second selected pressure (P2) that is below the first selectedpressure (P1) by a first selected amount, the computer being programmedto resume operation of the motor to resume moving the plunger to resumeflow of fluid to the needle point when the instantaneous pressure isbelow the first selected pressure (P1) by the first selected amount, thememory also storing a third selected pressure (P3) that is below thefirst selected pressure (P1) and above the second selected pressure(P2), the computer being programmed to again stop operation of the motorto stop moving the plunger to again stop flow of fluid to the needlepoint when the instantaneous pressure rises to the third selectedpressure (P3) after having reached the second selected pressure (P2). 4.The apparatus of claim 1, wherein said controller has an input forreceiving at least one parameter including at least the first selectedpressure (P1).
 5. The apparatus of claim 3, wherein said controller hasan input for receiving a plurality of parameters including at least oneof the first, second and third selected pressures (P1, P2, P3).
 6. Theapparatus of claim 1, wherein said first selected pressure (P1) isbetween about 25 mm/Hg and about 300 mm/Hg.
 7. The apparatus of claim 1,wherein said second selected pressure (P2) is between about 25 mm/Hg andabout 100 mm/Hg.
 8. The apparatus of claim 3, wherein said thirdselected pressure (P3) is between about 80 to about 180 mm/Hg dependingthe anatomic space, the first selected pressure (P1) being about 80 toabout 300 mm/Hg depending on the anatomic space and the second selectedpressure (P2) being about 20 to about 100 mm/Hg depending the anatomicspace.
 9. The apparatus of claim 4, wherein said at least one parameteris selected from the group consisting: of injection tubing length;injection tubing bore; injection fluid viscosity; injection fluidcomposition; and injection fluid temperature.
 10. The apparatus of claim1, wherein said pressure transducer is permanently connected in-line atthe connected between the opposite end of the syringe and the tubing.11. The apparatus of claim 1, wherein said drive unit has a housing witha syringe cavity for removably holding the body of the syringe in anaxially fixed position on the housing, and a plunger recess wherein theplunger is free to move, the syringe armature having a stage movablealong the plunger recess, the plunger having thumb pad and the stagehaving at least one pivotally mounted and spring-loaded hook forengaging the thumb pad when the stage is moved to engage the thumb padto axially connect the stage to the thumb pad so that movement of thestage in opposite directions moves the plunger in opposite directions,the syringe armature including a sensor for sensing that the stage hasbeen moved to engage the thumb pad, the computer being programmed tostop the movement of the stage under the influence of the sensor whenthe stage has engaged the thumb pad.
 12. The apparatus of claim 1,including a proprietary connector, electrically and mechanicallyconnected between the pressure transducer and the controller forallowing operation of the controller only if an authorized a disposablesassembly is connected to the pressure transducer.
 13. The apparatus ofclaim 1, wherein said needle point is adapted for insertion into one of:an epidural tissue space; an intra-articular space; an intra-occularfluid of a globe of an eye; an vessel of the body; and a tissue spacecomprised primarily of bodily fluids.
 14. The apparatus of claim 13,wherein said needle is a catheter needle.
 15. The apparatus of claim 1,wherein said injection fluid comprises a drug.
 16. The apparatus ofclaim 1, wherein said apparatus further comprises a visual signal, underthe control of said controller, wherein said visual signal indicateseach time said flow rate starts or stops.
 17. The apparatus of claim 1,wherein said controller further comprises an audible signal generatorunder the control of said controller, wherein said audible signalgenerator generates an audible indication each time the fluid flowstarts or stops.
 18. The apparatus of claim 1, wherein said disposablesassembly includes a rigid and elongated handle permanently connected tothe tubing, and for connection to the needle, the handle having a lengthof about 10 to 20 cm.
 19. A method for administering an injection into afluid filled tissue space, said method comprising: providing a testingfluid, an injection fluid, a pumping mechanism, and an end adapted forinsertion into said patient, pumping said testing fluid into saidpatient, calculating the fluid pressure of said testing fluid at aninterface between said end and the fluid filled tissue of said patient,controlling the flow rate of said injection fluid such that said fluidflow initiates once measured pressure drops below pre-set fluidpressure, identifying the loss-of-pressure associated with the entry ofsaid end into said fluid filled tissue space, and pumping said injectionfluid into said fluid filled tissue space.
 20. The method of claim 19,wherein said testing fluid is selected from the group consisting ofphysiological saline, phosphate-buffered saline, artificial cerebralspinal fluid, Ringers, 5% dextrose, and filtered air.